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Table 5 Gene-protein IHC (comparator) vs. single IHC (reference) agreement analyses

From: A gene-protein assay for human epidermal growth factor receptor 2 (HER2): brightfield tricolor visualization of HER2 protein, the HER2 gene, and chromosome 17 centromere (CEN17) in formalin-fixed, paraffin-embedded breast cancer tissue sections

Single IHC
  Gene-protein IHC Positive Negative Total
Reader A Positive 50 2 52
  Negative 0 131 131
  Total 50 133 183
  PPA: n/N (%) (95% CI) 50/50 (100.0) (92.9–100.0)   
  NPA: n/N (%) (95% CI) 131/133 (98.5) (94.7–99.6)   
  OPA: n/N (%) (95% CI) 181/183 (98.9) (96.1–99.7)   
  Kappa coefficient (95% CI) 0.97 (0.94–1.00)   
Reader B Positive 47 3 50
  Negative 1 132 133
  Total 48 135 183
  PPA: n/N (%) (95% CI) 47/48 (97.9) (89.1–99.6)   
  NPA: n/N (%) (95% CI) 132/135 (97.8) (93.7–99.2)   
  OPA: n/N (%) (95% CI) 179/183 (97.8) (94.5–99.1)   
  Kappa coefficient (95% CI) 0.94 (0.89–1.00)   
Reader C Positive 54 1 55
  Negative 0 128 128
  Total 54 129 183
  PPA: n/N (%) (95% CI) 54/54 (100.0) (93.4–100.0)   
  NPA: n/N (%) (95% CI) 128/129 (99.2) (95.7–99.9)   
  OPA: n/N (%) (95% CI) 182/183 (99.5) (97.0–99.9)   
  Kappa coefficient (95% CI) 0.99 (0.96–1.00)   
  1. IHC: immunohistochemistry; PPA: positive percent agreement; NPA: negative percent agreement; OPA: overall percent agreement.